|Publication number||US7023619 B2|
|Application number||US 10/872,213|
|Publication date||Apr 4, 2006|
|Filing date||Jun 17, 2004|
|Priority date||Jun 17, 2004|
|Also published as||US20050280905|
|Publication number||10872213, 872213, US 7023619 B2, US 7023619B2, US-B2-7023619, US7023619 B2, US7023619B2|
|Original Assignee||Hewlett-Packard Development Company, L.P.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (14), Classifications (9), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
Projector systems are generally devices that integrate light sources, optics systems, and electronics for front- or rear-projection of images from computers or video devices onto walls or screens, for large-image viewing. They are especially popular among business users who give presentations as part of their job responsibilities. Newer projectors can weigh as little as a few pounds, making them well suited for business travelers. As the quality of projection technology has improved, projectors are also finding their way into peoples' homes for high-definition television (HDTV) and other home entertainment applications.
One type of projection system is a digital projection system that utilizes spatial light modulators (SLM's) to project image data therefrom. Examples of SLM's include liquid crystal display (LCD) SLM's, and digital micromirror device (DMD) SLM's, Liquid Crystal on Silicon (LCoS) SLM's, as well as other types of SLM's. There may be one pixel on each SLM in the projector for each pixel of digital image data to be projected. The projection system controls the SLM pixel or pixels in accordance with the pixel of the image data to which the SLM pixel corresponds. The SLM pixel modulates the light that is incident to the SLM pixel in accordance with the image data pixel, and the projector projects the pixel.
Light sources when combined with reflectors and or lenses typically found in digital projection systems output converging, diverging or collimated light that, due to the nature of the light sources, is more bright at the center of the beam than at the edges of the beam. If this light from the source and the reflector is used to illuminate the SLM it will be too bright in the center of the SLM and dimmer around the edges. Left uncorrected, such light results in image projection that may be too bright at the center of the image and too dim at the edges of the image. To correct this problem, digital projection systems typically include illumination systems with complicated optics mechanisms that are made up of a number of lenses, mirrors, and/or condenser optics. The purpose of the illumination system is to capture light from the source and spatially homogenize the light so that it can provide essentially uniform illumination of the SLM, so that this can be imaged onto the screen for viewing. Even then, however, the problem is not completely corrected, and including such sophisticated illumination optics mechanisms raises the costs of digital projectors.
The drawings referenced herein form a part of the specification. Features shown in the drawing are meant as illustrative of only some embodiments of the invention, and not of all embodiments of the invention, unless otherwise explicitly indicated, and implications to the contrary are otherwise not to be made.
In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.
Digital Projection System
The light source(s) 104 of the light source mechanism 102 output light. Each of the light source(s) 104 may be an ultra high-pressure (UHP) mercury vapor arc lamp, xenon, or another type of light source. For instance, the light source(s) may be other types of light bulbs, as well as other types of solid state light sources such as light-emitting diodes (LED's), and so on. The light output by the light source(s) 104 is for ultimate modulation by the SLM pixels 110. The light output by the light source(s) 104 may be convergent, divergent or collimated, and is typically brighter at the middle or center than at the edges. The illumination optics mechanism 108 spatially homogenizes and guides the light as output by the light source(s) 104 to the SLM pixels 110 for correct modulation thereby.
The SLM pixels 110 may be liquid crystal display (LCD) SLM's, digital micromirror device (DMD) SLM's, as well as other types of SLM's. The number and configuration of the SLM pixels 110 enables the projection system 100 to realize a given resolution, such as a 4:3 aspect ratio such as 800×600 or 1024×768, or a 16:9 aspect ratio such as 1920×1080 or 1280×720. The controller 112 controls the SLM pixels 110 in accordance with the digital image data 116 that is received from the image source 120. The image source 120 may be a computing device, such as a computer, or another type of electronic and/or video device. The controller 112 in one embodiment particularly sets the SLM pixels 110 in accordance with the saturation intensity or other values of the pixels of the image data 116. Furthermore, the controller 112 may scale the image data 116 from one resolution to another, so that the resolution of the image data 116 ultimately conforms to that of the SLM pixels 110. Alternatively, the controller 112 may receive the image data 116 as having the same resolution as that of the SLM pixels 110.
The SLM pixels 110 ultimately modulate the light output by the light source(s) 104 in accordance with the image data 116 as controlled by the controller 112. The image data 116 may be a still image or a moving image, for instance. The projection optics mechanism 118 projects this light externally or outward from the projection system 100, where it is displayed on the screen 122, or another physical object, such as a wall, and so on. The screen 122 may be a front screen or a rear screen, such that the projection system 100 may be a front-projection system or a rear-projection system. The projection optics mechanism 118 guides the light as modulated by the SLM pixels 110 outward from the system 100. The user of the projection system 100, and other individuals able to see the screen 122, are then able to view the image data 116.
The projection system 100 is a digital projection system 100 because the SLM pixels 110 each modulate one pixel or sub-pixel of the digital image data 116 as presented to the SLM pixels 110 by the controller 112. As such, the light source(s) 104 output light, as affected by the illumination optics mechanism 108, to each of the SLM pixels 110. Where the light output by the light source(s) 104 is brighter at the center than at its edges, the resulting image projected from the system 100 onto the screen 122 is also brighter at the center than at the edges. Therefore, the illumination optics mechanism 108 is responsible for rendering illumination from the light source(s) 104 onto the SLM pixels 110 that it is at least substantially spatially uniform, so that the resulting image projected onto the screen 122 has substantially uniform brightness.
The shading of the digital image 250 is indicative of the brightness with which the digital image 250 is projected onto the screen 122, and corresponds to the brightness of the illumination profile 200 of
Concave Multi-Faceted Optical Mirror
That is, the facets of the reflectors 300 and 300′ divide the light 406 such that the resulting light that is incident upon the SLM pixels 110 is more uniform. The facets 306 effectively disperse the light incident upon the reflectors 300 and 300′ so that different components of the light are mixed, and the resulting light is more uniform in illumination when arriving at the SLM pixels 110. The greater the number of facets, the more mixing of the light that occurs, resulting in greater uniformity of the illumination of the light that arrives at the SLM pixels 110.
The mixing of the light by the reflectors 300 and 300′ can result in the output light as having overlapping beams when incident upon the SLM pixels 110, which also results in the greater uniformity of the illumination of the light that arrives at the pixels 110. Furthermore, the reflectors 300 and 300′ that renders the light from the light source(s) 104 more uniform when arriving at the SLM pixels 110 is different than other reflectors that are part of the light source mechanism 102 itself, and which may themselves be faceted. The reflectors 300 and 300′ in one embodiment of the invention can replace a large number of optical elements that would ordinarily be employed to render the light 406 more uniform, reducing the cost of the overall digital projection system 100.
That is, in one embodiment of the invention, the light 406 incident to the reflectors 300 and 300′ is not uniform. The reflectors 300 and 300′ serve to mix the light 406 becomes more uniform when incident upon the SLM pixels 110. That is, all of the light 406 is incident upon the reflectors 300 and 300′, which mix the light as a result of their facets, so that the light incident upon the SLM pixels 110 is more uniform. It is noted that the reflectors 300 and 300′ accomplish such mixing in a single reflection, or bounce, of the light 406. That is, each of the facets of the reflectors 300 and 300′ only reflects the light once, distributing the light via a single reflection. This is as compared to condenser optics found in conventional projection systems, such as a condenser rod, in which light is reflected, or bounced, multiple times while being transmitted through such the condenser rod. As a result, the efficiency of the reflectors 300 and 300′ is significantly greater than in such conventional systems. For instance, if it is assumed that reflecting light reduces the brightness of the light by 2%, the reflectors 300 and 300′ provide for 98% of the original brightness of the light to reach the SLM pixels 110. By comparison, within a conventional projection system, each bounce reduces the light output from the previous bounce by 2%. If there are seven bounces within a conventional condenser rod, then the efficiency of the rod is only 98%7=86.8%.
Furthermore, in an alternative embodiment of the invention, the reflectors 300 and 300′ just reflect a small portion of the light 406 that is relatively uniform, and expands that portion of the light 406 so that it is reflected onto all of the SLM pixels 110. For instance, the illumination profile 200 of
The facets 306 of the reflectors 300 and 300′ have been depicted in
Methods and Conclusion
It is noted that, although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and equivalents thereof.
|Cited Patent||Filing date||Publication date||Applicant||Title|
|US3620600||Apr 30, 1970||Nov 16, 1971||Ford Motor Co||Lens with facets for projecting light along different axes|
|US4021659||Oct 30, 1975||May 3, 1977||General Electric Company||Projector lamp reflector|
|US4512631||Apr 21, 1983||Apr 23, 1985||Rca Corporation||Rear projection television screen incorporating a prism lens|
|US4545000||Mar 25, 1985||Oct 1, 1985||Gte Products Corporation||Projection lamp unit|
|US5098184||Apr 30, 1990||Mar 24, 1992||U.S. Philips Corporation||Optical illumination system and projection apparatus comprising such a system|
|US5510861||Sep 15, 1994||Apr 23, 1996||Proxima Corporation||Compact projector and method of using same|
|US5704701 *||Mar 4, 1993||Jan 6, 1998||Rank Brimar Limited||Spatial light modulator system|
|US6102545||Oct 17, 1995||Aug 15, 2000||Hitachi, Ltd.||Liquid crystal display unit|
|US6344876||Nov 18, 1997||Feb 5, 2002||Canon Kabushiki Kaisha||Image blur preventing apparatus|
|US6356700||Jun 8, 1999||Mar 12, 2002||Karlheinz Strobl||Efficient light engine systems, components and methods of manufacture|
|US6621610||Apr 2, 2002||Sep 16, 2003||Seiko Epson Corporation||Light deflective optical system|
|US20020122157||Oct 22, 2001||Sep 5, 2002||Tetsuyuki Miyawaki||Projection-type display device|
|US20020154423||Apr 19, 2002||Oct 24, 2002||Hans-Erich Gubela||Reflective mirror structure comprised of a multiplicity of prisms|
|US20040012832||Oct 11, 2001||Jan 22, 2004||Gallen Niall Anthony||Beam expansion|
|U.S. Classification||359/618, 353/37|
|International Classification||G02B27/00, G02B17/00, G02B27/09|
|Cooperative Classification||G02B27/0983, G02B27/0905|
|European Classification||G02B27/09A, G02B27/09S3C|
|Jun 17, 2004||AS||Assignment|
Owner name: HEWLETT-PACKARD DEVELOPMENT COMPANY, L.P., TEXAS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:PATE, MICHAEL;REEL/FRAME:015496/0417
Effective date: 20040614
|Oct 5, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Nov 15, 2013||REMI||Maintenance fee reminder mailed|
|Apr 4, 2014||LAPS||Lapse for failure to pay maintenance fees|
|May 27, 2014||FP||Expired due to failure to pay maintenance fee|
Effective date: 20140404